Lubricant producing system



21, 1970 E- J BRETON ErAL LUBRICANT PRODUCING SYSTEM Filed June 28, 1968FIG-Z INVENTORS RNEY E N N O o l. T V v E R U... BM J E J T T 8 Dn E E NB R o E R Y B .M.

United States Patent 3,507,775 LUBRICANT PRODUCING SYSTEM Ernest J.Breton, Wilmington, and Robert E. Murvine, Newark, Del., assignors to E.I. du Pont de Nemours and Company, Wilmington, Del., a corporation ofDelaware Filed June 28, 1968, Ser. No. 740,879 Int. Cl. C08f 1/02; C08g35/00; C10g 41/00 US. Cl. 208-46 24 Claims ABSTRACT OF THE DISCLOSUREOne can avoid the necessity of adding lubricants to a variety of fluidprocess assemblies involving relatively movable opposing surfaces byselecting the particular alloys for the surfaces. Specifically, thelubricant can be formed in situ from the fluid used Where one surface isof an alloy containing at least 6 atom percent of an element selectedfrom the group consisting of molybdenum and tungsten, at least 10percent by volume of the alloy being an intermetallic compound ofmolybdenum or tungsten having a Vickers Hardness number of 550-1800; themating surface is either of an alloy containing at least 50 atom percentiron, at least 1 atom percent carbon, at least one-half the weight ofthe remainder of the alloy being composed of at least one of thefollowing elements: chromium, manganese, molybdenum and tungsten, saidelement(s) being present as carbide(s) or in a fully hardened solidsolution, and having a Vickers Hardness number of at least 400 or asimilar alloy containing at least 80 atom percent iron and having aVickers Hardness number of at least 200 or an alloy of 11-15 atompercent carbon, 1.5-3 atom percent silicon, the balance being iron,having a Vickers Hardness number of at least 150; and the fluid is anorganic compound capable of polymerizing to form a lubricant, e.g.,petroleum hydrocarbons, aliphatic alcohols, and aliphatic aldehydeshaving at least 4 carbon atoms.

CROSS REFERENCES TO RELATED APPLICATIONS This application is related toour copending application, Ser. No. 740,880, entitled Improved LubricantProducing System which was filed on the same date as the presentapplication.

BACKGROUND OF THE INVENTION This invention is in the field of functionalsystems producing lubrication.

Ideally, a lubricant for the interface of relatively movable (sliding,rubbing, rolling, etc.) opposing surfaces should serve to completelyseparate those surfaces. This condition is known as full-film orhydrodynamic lubrication. Full-film lubrication physically separates thetwo sliding surfaces by a relatively thick continuous film ofself-pressurized lubricant with no metal-to-metal contact.Technologically, this is the preferred kind of lubrication since itoffers the lowest coefficient of friction and the smallest amount ofwear.

When the two sliding surfaces are being rubbed together in the presenceof an extremely thin film of lubricant which adheres to both surfaces,this condition is known as complete boundary lubrication. Unless thelubricant is renewed periodically, the thin film is even- 3,507,775Patented Apr. 21, 1970 ICC tually destroyed and intimate metal-to-metalcontact results (dry operation) with the result being scoring andgalling of the metals, and eventually seizure.

A transitional zone known as mixed-film lubrication is a combination ofhydrodynamic and boundary lubrication. Under this condition, part of thetotal load applied to an opposing metal surface is supported byindividual loadcarrying areas of self-pressurized lubricant and theremaining part by the very thin film associated with 'boundarylubrication.

Under full-film conditions, the coeflicient of fluid friction isapproximately proportional to viscosity and speed and inverselyproportional to load. Where true boundary lubrication exists, thecoefficient of friction is independent of viscosity and rubbing speed.Thus for small values of ZN/p, where Z is the viscosity of the inputfluid, N is rotational speed and p is bearing pressure (load), thecoefficient of friction remains essentially constant. Between theboundary and full-film zones of lubrication is the zone where, withreduction of ZN/ p, the coeflicient of friction increases sharply.Evidence indicates that in this zone a combination of fluid friction andboundary lubrication exists, i.e., mixed-film lubrication.

When the speed (N) and viscosity (Z) are low, the load, which can beapplied to surfaces without attaining unduly high coeflicients offriction and the resultant catastrophic efiects thereof, mustnecessarily be very low. Hence, the use of low viscosity fluids aslubricants is precluded in most industrial applications since their useplaces a severe restriction on the load bearing capacity.

Lubrication of the opposing surfaces of seals, gears, bearings andpistons, therefore, has required the use of more viscous materials suchas hydrocarbon oils, synthetic oils and greases. These lubricants, inaddition to being incapable of being tolerated in certain applicationsbecause of process contamination, possess other disadvantages. Whenthese lubricants are used continuously over extended periods at highpressures and elevated temperatures, they tend to deteriorate. Sludgestend to form in the lubricants as a result of oxidation, polymerization,or other causes. These sludges reduce the lubricating qualities of thelubricant and often cause sticking of relatively moving parts. Inaddition, organic acids tend to form in the lubricant during usethereof, apparently because of oxidation of the oil at the elevatedtemperatures to which the oil is exposed, and organic acids causecorrosion.

Additional disadvantages exist where the operation of engines requiremixing oil with the fuel as in the 2-cycle engine and the epitrochoidalrotary engines. Smoke, fouling of the spark plugs, sticking of pistonrings, and carbon deposits result from the use of such mixtures.

It is apparent that great advantages could be obtained if the processfluid, e.g., gasoline in internal combustion engines, could itself beused for lubricating the opposing parts. Besides eliminating the needfor auxiliary systems for handling lubricant, the use of the processfluid for lubrication could lead to improved reliability and reductionin the size, weight and cost of the apparatus. Additionally, since thesefluids are being continuously used up in the operation of the particularprocess, contamination by such things as sludge formation would beminimized.

It is, therefore, the object of this invention to provide assembliescomposed of rolling element bearings, seals, sliding vanes, pistons,pistonrings, gears, etc. moving against opposing surfaces that willfunction in the presence of low viscosity organic agents. It is anotherobject to provide an assembly capable of converting in situ a lowviscosity organic fluid, e.g., gasoline vapor or liquid, unsuitable as alubricant in its unpolymerized state to a more viscous polymericmaterial characterized by its ability to maintain a state of boundarylubrication or fullfilm lubrication during periods of operation. It is afurther object to provide lubricant-producing assemblies for designingand constructing devices (engines, pumps, etc.) in which the problemsresulting from the conventional use of lubricants are eliminated.

SUMMARY OF INVENTION The objects are accomplished according to thepresent invention by an assembly comprising at least two members havingrelatively movable opposing surfaces, members A and B, and a fluidcapable of polymerizing to form a lubricant during operation of theassembly (a lubricant precursor); the metal-opposing surface of member Acomprising an alloy selected from the group consisting of (a) an alloyof 11-15 atom percent carbon, 1.5-3 atom percent silicon and the balancebeing substantially all iron, and having a Vickers Hardness number of atleast 150, (b) 1 an alloy of at least 80 atom percent iron and having aVickers Hardness number of at least 200, and (c) 1 an alloy of at least50 atom per cent (50-79 atom percent) iron and having a Vickers Hardnessnumber of at least 400, preferably the alloy of (a) or (b); themetal-opposing surface of member B comprising an alloy of at least 6,preferably at least 12, atom percent of an element selected from thegroup consisting of molybdenum and tungsten, at least percent,preferably 20-85 percent, by volume of the alloy being an intermetalliccompound of said element preferably in the topologically close packedphase, the Vickers Hardness number of the compound being 550-1800, andany matrix containing the compound having a Vickers Hardness number lessthan that of the compound, the coefficient of dry friction of theopposing surface of member B against the surface of member A being nogreater than 0.25; and the fluid being selected from the groupconsisting of petroleum hydrocarbons having a terminal boiling point nogreater than 345 C., aliphatic alcohols of 1-12 carbon atoms; andaliphatic aldehydes of 4-9 carbon atoms.

Specifically, assemblies of this invention can be formed that meet thecriteria set forth in the previous paragraph where one of the relativelymovable opposing surfaces comprises an alloy of 6-85, preferably 19-25atom percent molybdenum, 4-56, preferably 4-22 atom percent silicon andthe balance essentially 10-90 atom percent of an element selected fromthe group consisting of iron, cobalt and nickel, preferably 53-77 atompercent cobalt; the other of the relatively movable opposing surfacescomprising an alloy of l-7 atom percent carbon, up to 13 atom percentchromium and the balance essentially 80-98 atom percent iron; and thefluid selected from the previously stated group but being preferablygasoline. Where the first-mentioned relatively movable opposing surfacecomprises an alloy of tungsten, it may be diflicult to incorporate morethan 25 atom percent of tungsten into the alloy because of the highmelting point of tungsten.

It should be understood that in addition to molybdenum and tungsten inthe one opposing surface and iron in the other opposing surface, amountsof elements other than those specified above may be used in bothsurfaces provided that the criteria regarding the Vickers Hardnessnumbers, intermetallic compound and coefficient of dry Also containingat least 1 atom percent carbon, the sum of any cobalt and nickel beingless than 6 atom percent and wherein at least one-half of the weight ofthe remainder of the alloy is composed of at least one element selectedfrom the group consisting of chromium, manganese, molybdenum andtungsten, said element(s) present as a carbide(s) or in a fullyhardened. SQlid solution, e.g., the martensite phase of iron.

friction are met as set forth above. It is also possible to includeminor amounts of refractory metal oxides in the alloys such as thosedisclosed in US. Patent 3,317,285. In using the system of this inventionfor sliding elements, performance can be further improved by optimizingthe topography, the grooving and the clearance of both surfaces of thesliding couple.

Coefficient of dry friction, as used in the Summary Of The Invention, ismeasured in air, as follows:

The substantially flat metal-contacting surface of the member having thelower Vickers Hardness number (usually member B) is given ametallographic polish and washed with acetone to insure a smooth cleansurface. A -inch ball (or, alternatively, an object having a sphericalsurface radius of -inch) near its point of contact with the flatsurface, composed of the material of the harder member (usually memberA) is cleaned by polishing with 600 grit emery cloth. The testsample ofthe flat member is mounted on a moving track and passed at a speed of0.001 cm./sec. in contact with the ball of the second member. A load of1000 grams is imposed on the ball. The frictional drag created by thesample of the flat member moving in contact with the ball is measured bya tangential strain gauge. The value of dry friction is the tangentialforce required to move the test sample divided by the normal force,which in this case is 1000 grams.

For purposes of simplicity and clarity in illustrating the criticalfeatures of this invention, the discussion will be divided into threesegments;

(1) Metal-contacting or opposing surface of member B, also referred toas the lubricant producing (LP) alloy surface;

(2) Metal-contacting or opposing surface of member A, also referred toas the mating surface; and

(3) Environmental Medium, also referred to as the process fluid, carrierfluid or simply, the fluid.

LUBRICANT PRODUCING ALLOY SURFACE The important criteria for selectingthis alloy are in three distinct areas: chemical composition; physicalstructure; and physical characteristics. As for chemical composition,the alloy should contain at least 6 atom percent of molybdenum ortungsten. As for physical structure, it should be composed of at least10 percent by volume of an intermetallic compound having molybdenum ortungsten as a component. The physical characteristics should be suchthat the alloy has a coeflicient of dry friction when contacted againstthe mating surface of no greater than 0.25; the intermetallic compoundof the alloy has a Vickers Hardness number ranging between 550 and 1800;and, when present, the matrix containing the intermetallic compoundshould have a Vickers Hardness number less than that of theintermetallic compound.

When used in the present invention, the aforementioned alloys will becapable of producing lubricant when subjected to sliding action in thepresence of a fluid capable of being converted into a material havinglubricating properties. Specifically, when subjected to 50,000 PV (loadin p.s.i. velocity of 180 ft./min. or greater) in the wear tester shownin FIGURE 1, the total wear of both lubricant producing alloy (sample)and mating surface (reference ring) will be less than 4.0 mils/ hrs. asmeasured by micrometer or weight measurements; and the coefficient offriction will be less than 0.2. The test procedure, as set forthhereinafter, was designed so that operating conditions would lead to astate of lubrication below that of the full-fluid range, thus obtainingmetalto-metal interaction. In this way, the compatibility and ability ofthe metal combinations to produce lubricant can be measured. It isbelieved that the lubricant i not produced continuously in the system ofthe invention. Instead, additional lubricant is only produced after thatoriginally formed is used.

FIGURE 1 is a schematic representation of the Wear tester utilized indetermining wear performance. It is representative of end thrust typebearings and is useful as a screening device for determining systems ofthe present invention. The specimen of number A to be tested 12 isrotated by a DC motor 10. The friction between the ring of member B11and the test specimen of member A 12 produces a torque in the shaft 13.The shaft 13 is constrained from turning by the lever arm 14 connectedto a strain gauge 15. The strain gauge voltage is continuously monitoredon a recorder. This voltage is converted into pounds pull by previouscalibration. From the geometry of the system, the tangential force onthe specimen is calculated. The coefficient of friction equals thetangential force divided by the normal thrust of load pushing thespecimen and wear ring together. Wear rates are deter mined from weightloss and also by micrometer measurements. Tests are carried out byrotating the test specimen at a speed of 180 ft./min. and at'varyingloads. The PV is determined by multiplying the load in p.s.i. based uponactual contact area by the speed in ft./min.

Specifically, the specimen 12 and the ring 11 are machine ground toobtain parallel faces and then hand lapped on 400 grit paper; vacuumdried at 100 C. for at least 1 hour; and then weighed to 0.0001 gram andmeasured to 0.0001 inch. They are then mounted in the tester as shown inFIGURE 1 and the cup 16 filled with gasoline or other fluid 17. The cup16 is lined with cooling coils to minimize evaporation. Using only theweight of the shaft 13 and lever 14, the tester is run at 650 rpm. (toprovide 180 ft./min.) for 1 to 2 minutes. After this 6 run minutes ateach weight increment until failure occurs.

In the following examples, a series of alloys were tested in the deviceshown in FIGURE 1. The results illustrate the importance of the criteriaset forth previously for the lubricant producing alloy surface.

Examples 1-10 The test specimens were prepared from the elements setforth in Tables I-A and LB by mixing, melting and casting them intobuttons 1% inches in diameter and inch thick. The buttons were machinedto fit the wear tester shown in FIGURE 1. All except the composition ofExample 7 were tested using Elastuf 44 steel 2 composed of 2.1 atompercent carbon, 1 atom percent chr0- mium, 0.3 atom percent molybdenum,0.4 atom percent silicon, 0.9 atom percent sulfur and the balance, 93.6atom percent, iron as the ring; and liquid gasoline as the fluid. InExample 7, the ring was composed of an alloy of 95.7 atom percent ironand 4.3 atom percent carbon hardened to a Vickers Hardnes number of 510.

The results obtained for the examples are shown in Table I-A and, forcomparison, the results for 11 controls, Controls A-K, are shown inTable I-B. It should be noted that although the materials used inControls C-J contain at least 6 atom percent molybdenum with at last oneother element, some of which might form intermetallic compounds withmolybdenum, these materials did not contain at least 10 volume percentof any intermetallic compound.

TABLE I-A Vickers Total Chemical Composition Coeflicient Hardness No.Wear (atom percent) of Inter- Coefficient (mils/ Dry metallic PV 100 M000 Fe Ni Si Friction Compound Friction X1, 000 hrs 1 All materials usedin the examples contain at least 10 volume percent of an intermetalliccompound of molvhdenum.

1 Heat treated 4 hours at 480 C.

3 Also contained 5 atom percent silver. 4 Also contained 12 atom percentchromium.

1 None of the materials used in the controls contained at least 10volume percent of an lntermetallic compound of molybdenum.

1 Also contained 21.1 atom percent chromium, 3.6 atom percent titaniumand 3.2 atom percent aluminum.

3 Also contained 19 atom percent chromium and 2 atom percent tungsten.

period, the preselected load, is applied and the test is runcontinuously for 18 to 20 hours. Due to evaporation, additional fuelmust be added evry 4 to 6 hours. After 18 to 20 hours, the specimen 12and the ring 11 are again vacuum dried; weighed; and measured.Alternatievly, the tester may be loaded in increments of.20 lbs. whilebeing run at the previously disclosed speed. The tester may be 75Examples 11-14 In the examples, tungsten was used in place ofmolybdenum. The test specimens were prepared and tested following theprocedure set forth in Examples 1-10. The results obtained are comparedto the results obtained with four controls in Table II.

2 Manufactured by Horace T. Potts (30., Philadelphia, Pa.

TABLE II Vickers Total Chemical Composition Coefficient Hardness No.Wear (atom percent) of of Inter- Coefficient (mrls/ Dry metallic of PV100 Mo Fe Ni Si Friction Compound Friction X1, 000 hrs.)

xam 1 E nples 0, 23 1, 000 0.13 320 0. 6 0. 09 600-900 0. 11 760 0. 8 0.11 600-900 0. 10 560 a 0. 1 0. 08 800-1, 150 0. 11. 280 1..5

0. 11 2, 500-2, 600 0. 50 980 33. 7 0.37 Seized I 0.23 Seized Seized 1All materials used in the examples contain at least 10 volume percent ofan intermetallic compound of tungsen. g 2 These materials did notcontain a least 10 volume percent of an mtermetalllc compound oftungsten.

3 Also contained 50 atom percent carbon, i.e., as tungsten carbide.

4 Also contained 5 atom percent chromium, 4 atom percent carbon and 1atom percent vanadium. 5 Also contained 5 atom percent chromium, 4 atompercent carbon and 2 atom percent vanadium.

I From the foregoing examples and controls, it will be 20 columbium andtantalum, is a known promoter or stabilapparent that the presence of atleast volume percent of an intermetallic compound of molybdenum ortungsten in the contacting surface of member B is vital to theoperability of the present invention. These intermetallic compounds, inmost cases, occur as an intermediate or secondary phase within the solidsolution or matrix phase. They vary in amount and size and are ofdiverse types. The amount and type is determined by such factors as theparticular chemistry of the metals being alloyed, the length of time atwhich the alloy is subjected to specific temperature conditions, and thecooling rate. Interrnetallic compounds found in the alloys operable inthis invention include (1) the topological close packed (TCP) structuresincluding the sigma, Chi, Mu and Laves phases, (2) the semi-carbides ofthe M C and M C type and (3) MoSi type. The presence and amount ofintermetallic compounds may be determined by either X-ray diffraction ormetallographic analysis. For example, in Example 6 (Co/Mo/Si77/ 19/4)there is present 20 volume percent Laves phase, an intermetalliccompound. Example 9 is a pure intermetallic compound (MoSi with nomatrix.

If the relatively soft matrix is present, it has been observed that thismatrix portion wears preferentially leaving the hard intermetalliccompound in relief. It is believed that the fluid and lubricant formedcollect in the micro-cavities which are sufilciently close to providesuperior lubrication at the areas of member B that undergo sliding orrolling action with opposing areas of member A. 1

Of primary interest for this invention are the intermetallic compoundsof Laves phase structures characterized by the ternary phase systems,Co-Mo-Si, Ni-Mo-Si, Co-W-Si and Ni-W-Si. These alloys are disclosedin-U.S. Patent 3,257,178 to Severns and Smith and represent the mostdesirable alloys for use as the metal-opposing surface of member B.Specifically, these alloys are defined in this patent as consistingessentially of a substantial amount of at least one metal A andasubstantial amount of at least one metal B, and silicon, metal A beingselected from the group consisting of molybdenum and tungsten and metalB being selected from the group consisting of .cobalt and nickel; thesum of the amounts of metals A and B'being at least 60 atom percent ofthe alloy; the amount of silicon and the relative amounts of metals Aand B being such as to provide -85 volume percent of said alloy in theLaves phase; the Laves phase being distributed in a relatively softmatrix of the remaining 7015 volume percent of said alloy. 1

'The critical necessity for having the requisite amoun of intermetalliccompound present may be dramatically shown by comparing Example 2 withControl E. In both alloys, 9 atom percent of molybdenum is presentwithiron as the major constituent. In the case of an acceptable alloy inExample 2, however, 10 atom percent of silicon is also present. Thesilicon, which along with vanadium,

izer of intermetallic compounds in metal alloys, forms a ternaryintermetallic compound in excess of 10 volume percent. Similarly, thebinary iron-molybdenum alloy in the, atomic ratios shown in Controls Band C doesnot have the requisite amount of an intermetallic compound.Comparison of the data obtained shows that the binary alloy of theControls produces a high dry friction coefiicient and seizes against themating surface in the wear tester, while the ternary compound in Example2, although containing a like amount of molybdenum, is a satisfactorylubricant producing alloy. Similarly, whereas the molybdenum-cobaltbinary alloy (Control J) did not contain at least 10 volume percent ofan intermetallic compound, the ternary Mo-Co-Si alloys of Examples 6 and7 formed intermetallic compounds (Laves phase) in excess of 10 volumepercent.

One exception to the foregoing discussion is apparent in Control L ofTable II. Tungsten carbide, which is classified as an intermetalliccompound by the present definition, does not operate in the presentinvention. Although this material displays an extremely high wearresistance,'it also is characterized by a Vickers Hardness number inexcess of 2500. This hardness results in excessive wear of the matingmaterial (member A) rather than lubrication.

It should also be noted that Controls G and I, which are Hastelloy B andC, respectively, and Control D are similar in chemical composition tothe operable compositions of this invention. However, since Hastelloy Band C are designed for corrosion resistance, and Control D is designedfor high temperature operation, the molybdenum and tungsten aremaintained in solution in the matrix phase rather than in compounds. Asdiscussed by Streicher in Corrosion vol. 19, No. 8 August 1963, pp.272-284, the formation of molybdenum or tungsten compounds, e.g., Lavesor sigma phases, tends to accelerate corrosion and, as discussed bySimms in Journal of Metals, October 1966, pp. 1119-4130, the-formationof these compounds is undesirable for high temperature application.Without the formation of intermetallic compounds, these materials do.not function in the present'invention.

MATING'SURFACE J The important criteria for selecting the material forthe mating surface of member A are in' two distinctages: chemicalcomposition" and physical characteristicsfThe particular materials may'bedivided into three groups, the first two being preferred. V v

The first group embraces the cast irons containing .graphite They arethe gray cast irons and malleable cast ironsqCarbon content varies from11 to 15 atom'percent, and silicon content from 1.5 to 3"atom'percentwithjthe balance being' iron and trace amountsof othermetals.Hardnesses can be as low as Vickers Hardness numbers of 150. It isbelieved that the presence of.the carbon as graphite oflsets the effectof softness. These alloys are useful as piston rings, cylinder walls andin other applications having poor lubrication.

The second group consists of iron alloys containing at least 80 atompercent iron, at least 1 atom percent carbon and having Vickers Hardnesnumbers of at least 200. This group embraces the white cast irons,carbon steels, most of the tool steels and the bottom of the range ofmartensitic stainless steels. It is preferred that the Examples 21-23The test specimens were prepared and tested following the procedure setforth in Examples 1-10. As the lubricant producing alloy, the alloy ofExample 6 was used; namely, 77 atom percent cobalt, l9 atom percentmolybdenum and 4 atom percent silicon. The results obtained are comparedto the results obtained with two controls in Table IV.

I Also contained 0.3 atom percent molybdenum, 0.4 atom percent; silicon,0.9 atom percent manganese and 1.7 atom percent sulfur.

2 Also contained 13 atom percent cobalt.

3 Also contained 0.6 atom percent molybdenum.

Vickers Hardness number of the steels in this group be over 270.

The third group consists of iron-base alloys containing 50-79 atompercent iron, at least 1 atom percent carbon and having Vickers Hardnessnumbers of at least 400. Also undesirable are the ferritic stainlesssteels and most of the austenitic stainless steels. However, it maybepossible to use work hardened low nickel alloys of austenitic stainlesssteels.

The major alloying elements for the second and third groups arechromium, manganese, molybdenum and tungsten. These elements shouldrepresent at least one-half of the weight of the remaining alloyingelements (besides iron and carbon) and should be present primarily ascarbide precipitates or in a fully hardened solid solution, e.g., themartensite phase of iron. Nickel and cobalt are undesirable and theirsum in the alloy should be less than 6 atom percent.

In the following example, a series of mating surfaces were tested in thedevice shown in FIGURE 1. The results illustrate the importance of thecriteria set forth previously for the mating surface.

Examples 15-20 The test specimens were prepared and tested following theprocedure set forth in Examples l-lO. As the lubricant producing alloy,the alloy of Example 7 was used; namely 56 atom percent cobalt, 22 atompercent molybdenum and 22 atom percent silicon. The results obtained arecompared to the results obtained with four controls in Table From theforegoing examples and controls, the necessity for a minimum VickersHardness Number of 200 when at least atom percent iron is present in themating surface will be apparent. Controls B-F, when contrasted toExamples 18 and 19, bring out the importance of the minimum content ofiron in the surface. The failure of relatively soft materials isillustrated in Control A.

ENVIRONMENTAL MEDIUM The most impressive feature of the system of thisinvention is its ability to polymerize certain fluids to form lubricantsin situ, thereby obviating the necessity of using an extraneous(non-essential to the function of the system) material such as heavypetroleum products (e.g., motor oils, lubes, and greases). Bectuse oftheir commercial interest, the invention is concerned primarily withsystems involving petroleum hydrocarbon fuels as the environmentalmedium. Thus, gasoline in automotive, marine, and aircraft engines;kerosene and jet fuels in modern jet aircraft; and diesel fuels indiesel type engines are particularly useful in this invention. Thesefluids may be classified as petroleum hydrocarbons whose terminalboiling points are no greater than 345 C.

In Examples 1-23, gasoline was used as the environmental medium,gasoline being representative of petroleum hydrocarbons having aterminal boiling point no greater than 345 C. In the following examples,Examples 24-30, other fluids of lesser commercial interest were testedfollowing the procedure set forth in the previous examples. Thecombination of alloys used in Examples 11 7 and 15 were used; namely, 56 atom percent cobalt, 22

TABLE III Chemical Composition Total (atom percent) V1ckers WearHardness Coeflicient PV (mils/ Fe 0 Cr Mo V Number of Friction X1,000hrs.)

Examples:

80 0. 15 315 5. 2 225 0. 12 43 36 Seized 155 Seized Also contained 9atom percent nickel, 2 atom percent silicon and 2 atom percent manatompercent molybdenum and 22 atom percent silicon as the lubricantproducing alloy and 95.7 atom percent iron and 4.3 atom percent carbonas the mating surface alloy. The results obtained are set forth in TableV.

TABLE V Total Coefficient Wear Environmental v of PV (mils/ MediumFriction X1, 000 100 hrs.)

Examples 24 Methyl alcohol 0. 14 100 0.3 Ethyl alcohol 0. 11 400 1. 1n-Butyl alchoo 0. 12 300 0. 5 n-O ctyl alcohol 0. 500 0 28 Butyraldehyde0. 13 100 1. 0 29 10 wt. percent ethyl 0.05 50 0. 2

' alcohol, 90 wt. percent trichloroethylene. 30 10 wt. percent n-butyl0.02 50 1. 4

alcohol, 90 wt. percent trichloroethylene. Control. Trichloroethylene 0.3 27 44 It should be noted in Examples 29 and 30 that as little as 10weight percent of a fluid operable in this invention in combination with90 weight percent of an inoperable fluid (Control) will operatesuccessfully as part of the system of this invention. It should also bepointed out the systems of this invention will operate in the presenceof conventional lubricants (solid or fluid) and hydraulic fluids andwill thus make possible the use of lesser quantities of such addedlubricant. Furthermore, the systems of this invention could permit theuse of mixtures or dispersions of the specified hydrocarbons, alcoholsand aldehydes with such fluids as trichloroethylene, water, etc. whichare not usually considered lubricants. The use of the systems of thisinvention make it possible to use hydraulic fluids of relatively lowviscosity. During operation, the viscosity of the lubricants producedfrom these fluids is high enough to perform a lubricating function. Incold weather operation, the viscosity of the hydraulic fluid is lowenough so that no heating is required to maintain fluidity as is usuallynecessary with more viscous fluids.

Although in the examples the fluids have been used in liquid form, thefluids have also been used in vapor form. One method to achieve theresults of the present invention is to spray gasoline vapor into thechamber containing the relatively movable opposing surfaces.

Examples 313 2 FIGURE 2 illustrates a device utilized to test theefficiency of certain type bearings intended for commercialapplications. Referring to this schematic sketch, friction between shaft21 and the bearing to be tested 22 causes a yolk 23 to rotate when aload 24 is applied. The rotation of the yolk applies a force to a torquetransducer 25 through lever arm 26. From the torque which is recorded ona chart recorder, not shown, the tangential force acting at the bearingshaft interface is calculated. This divided by the load applied givesthe coeflicient of friction. The transducer is calibrated before eachtest. The process fluid, in this case gasoline, is introduced into thebearing system through port 27.

The test procedure involves increasing the flow of gasoline to 1 lb. perhour, at no load and then increasing the r.p.m. of the shaft to thedesired level. The load is applied in increments of 20 lb. and theapparatus allowed to run from minutes to an hour at each step.

The two types of bearings tested were roller bearings (inner and outerraces) in Example 31 and journal bearings in Example 32:

Example 31 Inner and outer races for roller bearings were made bycentrifugally castingan alloy of 77 atom percent cobalt, 19 atom percentmolybdenum and 4 atom percent silicon to nominal dimensions. The finaltolerances were obtained by grinding.

The roller bearing test was carried out by'nsing -the cast inner andouter races and commercially available rollersof hardened steel (SAE52100) Thenominal inside diameter of'the outer race was 0.901 inch andthe outside diameter of the inner race was 0.742inch. The rollers were0.078 inch in diameter and 0.612 inch long. The results of tests on theroller bearing described above and tests on a control using a rollerbearing having hardened steel (SAE 52100) inner and outer races aregiven in Table VIJAs can be seen from the table, the steel-steel rollerbearing system failed at 3600 r.p.m. at a'load' of 600 lbs'.; while thesystem of Example 31 wasstill operating efliciently at a load of 1000lbs. Additionally can be seen, that even at' smaller loads, thecoelficient'of friction in the system of Example 31 is significantlyless than that of the steel races.

Example 32 Journal bearings were fabricated by centrifugally casting analloy of 56 atom percent cobalt, 22 atom percent molybdenum and 22 atompercent silicon. The norminal size of the journal bearings was 0.752inch and the shaft of hardened steel (SAE 52100) was 2 mils undersize'to give the recommended clearance'for this size bearing. The journalswere rough machined used carbide tools to within 10 mils of finaltolerances and then ground the rest of the way.

Tests using a shaft speed of 1200 r.p.m. were conducted on the castCoMoSi bearing using the bearing tester in the manner describedhereinbefore. A journal bearing of the same dimensions was fabricatedfrom bronze SAE 660 4 and tested as a control under the same conditions.The performances of the two bearings are described in Table VII.

As shown in the table, the bronze bearing seized at the first incrementof loading. The cast CoMoSi bearing was loaded to a PV of 100,000 withno seizure.

' Control (SAE 52100) Races Example 31 (COMOSl) I Races Load at 3600,r.p.m. in lbs.

TABLE VII Coefficient of Friction Control (Bronze SAE 660) 1 Example 32(Cast CoMoSi) Seized Example 33 SAE 52100: 93.2 atom percent Fe; 4.4atom percent C; 11/51 atom percent Cr; 0.6 atom percentYSi 0.3 atompercent Bronze SAE 660 atom percent Cu; 4 atom percent Sn; 4 atompercent Zn 2 atom percent Eb. CM 5535: 56.4 atom percent.Co; 22.1 atompercentMo; 21.5 atom percent Si. 8 SAE 660 90 atom percent Cu 4 atompercent Sn; 4atom percent Zn 2 atom percent Pb.

Elastutt 44: 93.6 atom percent Fe 2.1 atom percent C; 1 atom percent Cr;0.9 atom percent S; 0.4, atom percent St; 0.3 atom percent Mo.

13 um base oil. Operating at 1000 rpm. and a PV of 140,000 the testseries was started at a dilution of 200 parts by volume water to onepart oil. The bronze seized at this concentration. The gray cast ironbegan stick-slip at 800 to 1 dilution and seized at 1600 to 1. CM 5535ran well through 1600 to 1 and seized at 3200 to l.

USES OF THIS INVENTION The assemblies of this invention findapplicability in all types of engines: 2- and 4-cycle reciprocatingengines; 2- and 4-cycle rotary engines including the epitrochoidal,elliptical, wedge and vane piston types; free piston gas generatingengines; turbo-jet engines; standard jet engines; and gas turbineengines. Thus, in a 2-cycle reciprocating engine, the bearing surfacesand seals can be composed of or coated with alloy of molybdenum ortungsten referred to herein as the member B alloy; while the opposingsurfaces including the crankshaft, the piston cylinder wall, etc. can becomposed of the alloy of iron referred to herein as the member A alloy.In an actual test of such an engine in which the connecting rod bearinghad a CM 7028 8 outer race, a case-hardened shaft of AISI E-4615 9 asthe inner race and AISI 1090 steel needles hardened to a RockwellHardness of over 55, there was no measurable wear.

The assemblies are also useful in fuel pumps and fuel injectors. Thus,in the fuel injectors the member B alloy can be used as a surfacecoating for the plunger which slides through a chamber made of member A,or member B can be used as a coating for the cylinder chamber throughwhich a plunger made of or coated with member A slides. In a fuel pump,the vanes can be coated with or composed of the member B alloy whichmakes contact with a chamber of member A, or visa versa. This permitsoperation with low viscosity fuels such as gasoline or kerosene. Thisopens up the possibility of operating' diesel engines with less viscousfuels than are now used.

A particularly interesting application of the present invention is inthe rotary internal combustion engine described in US. Patent 3,359,953.This patent describes special techniques to overcome the side sealingproblem. A coating of member B alloy of the present invention has beenused on the contacting surface of the ring seals in the side sealassembly of such a rotary engine while contacting end walls composed ofmember A alloy. It is apparent that the member B alloy of the assemblyof the present invention would be useful as the contacting surface ofall the end face seals while the inner surface of the end walls wascomposed of the member A alloy.

Another interesting application of the present invention is as asolution to the problem of increasing the load bearing capacity of oilimpregnated porous bearings, i.e., selflubricating bearings. Relativelylarge pores are needed in these bearings to transmit the relativelyviscous lubricant, thereby reducing load bearing capacity. By using alow viscosity precursor that forms a high viscosity lubricant in situ onthebearing surface, smaller pores would be used. This, in turn,increases the load bearing capacity of the bearing. By using the memberB alloy in the bearing along with the environmental media set forth forthis invention, greases having greater viscosity than conventional oilsare produced with an accompanying increase in load bearing capacity.

To summarize, the assemblies of this invention will be useful in amultitude of situations involving the use of bearings, gears, seals andpistons, the members of the assemblies being used either to form theparts or as coatings "CM 7028: 77 atom percent Co; 19 atom percent Mo; 4atom percent Si.

9 AISI 4615 97 atom percent Fe; 1.7 atom percent Ni: 0.7 atom percent C;0.5 atom percent Mn; 0.1 atom percent Mo.

AISI 1090: 95 atom percent Fe; 4.1 atom percent C; 0.7 atom percent Mn0.1 atom percent 1? 0.1 atom percent S.

for such parts. Thus, in our copending application Ser. No. 740,880,filed on the same date as this application, the piston rings in Example3 of that application were coated with the composition of the member Balloy of the present invention.

The following listing of uses is not intended to be limitative butintended to apprise those skilled in the art of useful applications ofthis invention.

LISTING OF END USES (I) General Bearings (A) Ball bearings:

Deep-groove Filling notch Angular contact Magneto Self-aligningMiniature Double-row (8) Duplex (9) Ball thrust (10) Seals and shieldsRoller bearings: (1) Cylindrical (2) Spherical (3) Tapered (4) Needle(pin) Journal bearings: (1) Bushings (2 Wick-oil (3) Oval-ring (4)Pressure-fed (5) Circumferential groove (6) Cylindrical (7) Cylindricalovershot (8) Pressure (9) Multiple-groove 10) Elliptical (11) Three-lobe(l2) Pivoted shoe (l3) Partial (14) Externally pressurized (D) Thrustbearings:

(l) Flat-land (2) Tapered land (3) Pivoted shoe (4) Step (5) Externallypressurized (6) Pocket (7) Standardized bushings (8) Slewing rings (II)Specific Bearings (III) Specific Gears Transmissions-automotive, farmmachinery Milling machinery Lathes Differentials Gear reducers PlanetaryHigh speed quills Splines (IV) Seals Rotary engines Piston rings1nternalcombustion engines Chemical pumps Fuel pumps (V) Pistons Internalcombustion engines Hydraulic equipment (3) Fuel Injectors and pumps (4)Positive displacement type fuel pumps What is claimed is:

1. A system comprising an assembly of at least two members, members Aand B, having relatively movable opposing surfaces and an environmentalfluid capable of forming a lubricating medium for said opposing surfacesduring operation of the assembly; the Opposing surface of member Aconsisting essentially of an alloy selected from the group consisting of(a) an alloy of 11-15 atom percent carbon, l.5-3 atom percent siliconand the balance being substantially all iron, and having a VickersHardness number of at least 150 (b) an alloy of at least 80 atom percentiron, at least 1 atom percent carbon, and having a Vickers Hardnessnumber of at least 200, and (c) an alloy of 50-79 atom percent iron, atleast 1 atom percent carbon, and having a Vickers Hardness number of atleast 400, the sum of any cobalt and nickel in said alloys (b) and (c)being less than 6 atom percent, at least one-half of the weight of theremainder of alloys (b) and being selected from the group of elementsconsisting of chromium, molybdenum, manganese and tungsten, saidelement(s) being present as carbide(s) or in a fully hardened solidsolution; the opposing surface of member B consisting essentially of analloy of at least 6 atom percent of an element selected from the groupconsisting of molybdenum and tungsten, at least 10 percent by volume ofsaid alloy being an intermetallic compound of said element, the VickersHardness number of said compound being 550-1800, and any matrix in saidalloy containing said compound having a Vickers Hardness number lessthan that of said compound, the coeflicient of dry friction of saidsurface of member B against said surface of member A being no greaterthan 0.25; and said environmental fluid being selected from the groupconsisting of petroleum hydrocarbons having a terminal boiling point nogreater than 345 C., aliphatic alcohols of 1-12 carbon atoms andaliphatic aldehydes of 4-9 carbon atoms.

2. A system as in claim 1 wherein said opposing surface of member A isan alloy of 11-15 atom percent carbon, 1.5-3 atom percent silicon, thebalance being substantially all iron, having a Vickers Hardness numberof at least 150.

3. A system as in claim 1 wherein said opposing surface of member A issaid alloy of at least 80 atom percent iron having a Vickers Hardnessnumber of at least 4. A system as in claim 1 wherein said opposingsurface of member B consists essentially of an alloy of at least 12 atompercent of an element selected from the group consisting of molybdenumand tungsten.

5. A system as in claim 4 wherein said element is molybdenum.

6. A system as in claim 4 wherein said element is tungsten. I

7. A system as in claim 1 wherein the intermetallic compound in thealloy of said opposing surface of member B is -85 percent by volume ofthe alloy.

8. A system as in claim 1 wherein said opposing surface of member Bconsists essentially of an alloy of 6-85 atom percent molybdenum, 4-5 6atom percent silicon, the bal- 16 ance being selected from the groupconsisting of iron, cobalt and nickel.

9. A system as in claim 1 wherein said opposing surface of member Bconsists essentially of an alloy of 19-25 atom percent molybdenum, 4-22atom percent silicon and 53-77 atom percent cobalt.

10. A system as in claim 1 wherein said environmental fluid is apetroleum hydrocarbon having a terminal boiling point no greater than345 C.

11. A system as in claim 1 wherein said environmental fluid is gasoline.

12. A system as in claim 1 wherein oil is added to said environmentalfluid.

13. An assembly comprising at least two members, members A and B, havingrelatively movable opposing surfaces; the opposing surface of member Aconsisting essentially of an alloy selected from the group consisting of(a) an alloy of 11-15 atom percent carbon, 1.5-3 atom percent siliconand the balance being substantially all iron, and having a VickersHardness number of at least 150, (b) an alloy of at least atom percentiron and having a Vickers Hardness number of at least 200, and (c) analloy of at least 50 atom percent iron and having a Vickers Hardnessnumber of at least 400, the sum of any cobalt and nickel in said alloys(b) and (c) being less than 6 atom percent, at least one-half of theweight of the remainder of alloys (b) and (c) being selected from thegroup of elements consisting of chromium, molybdenum, manganese andtungsten, said element(s) being present as carbide(s) or in a fullyhardened solid solution; and the opposing surface of member B consistingessentially of an alloy of at least 6 atom percent of an elementselected from the group consisting of molybdenum and tungsten, at least10 percent by volume of said alloy being an intermetallic compound ofsaid element, the Vickers Hardness number of said compound being550-1800, and any matrix in said alloy containing said compound having aVickers Hardness number less than that of said compound, the coefficientof dry friction of said surface of member B against said surface ofmember A being no greater than 0.25.

14. An assembly as in claim 13 wherein said opposing surface of member Ais an alloy of 11-15 atom percent carbon, 1.5-3 atom percent silicon,the balance being substantially all iron, having a Vickers Hardnessnumber of at least 150.

15. An assembly as in claim 13 wherein said opposing surface of member Ais said alloy of at least 80 atom percent iron having a Vickers Hardnessnumber of at least 16. An assembly as in claim 13 wherein said opposingsurface of member B consists essentially of an alloy of at least 12 atompercent of an element selected from the group consisting of molybdenumand tungsten.

17. An assembly as in claim 16 wherein said element is molybdenum.

18. An assembly as in claim 16 wherein said element is tungsten.

19. An assembly as in claim 13 wherein the intermetallic compound in thealloy of said opposing surface of member B is 20-85 percent by volume ofthe alloy.

20. An assembly as in claim 13 wherein said opposing surface of member Bconsists essentially of an alloy of 6-85 atom percent molybdenum, 4-56atom percent silicon, the balance being selected from the groupconsisting of iron, cobalt and nickel.

21. An assembly as in claim 13 wherein the opposing surface of member Bconsists essentially of an alloy of 19-25 atom percent molybdenum, 4-22atom percent silicon and 53-77 atom percent cobalt.

22. A process for forming a lubricating medium which comprises placingthe surfaces of at least two members, members A and B, in opposition,the opposing surface of member A consisting essentially of an alloyselected from the group consisting of (a) an alloy of 11-15 atompercent, 1.5-3 atom percent silicon, the balance being substantially alliron, having a Vickers Hardness number of at least 150, (b) an alloy ofat least 80 atom percent iron and having a Vickers Hardness number of atleast 175, and (c) an alloy of at least 50 atom percent iron and havinga Vickers Hardness number of at least 400, the sum of any cobalt andnickel in said alloys (b) and (c) being less than 6 atom percent, atleast one-half of the Weight of the remainder of alloys (b) and (c)being selected from the group of elements consisting of chromium,molybdenum, manganese and tungsten, said element(s) being present ascarbide(s) or in a fully hardened solid solution; and the opposingsuface of member B consisting essentially of an alloy of at least 6 atompercent of an element selected from the group consisting of molybdenumand tungsten, at least 10 percent by volume of said alloy being anintermetallic compound of said element, the Vickers Hardness number ofsaid compound being 550-1800, and any matrix in said alloy containingsaid compound having a Vickers Hardness number less than that of saidcompound, the coefficient of dry friction of said surface of member Bagainst said surface of member A being no greater than 0.25; adding afluid in a manner such that it flows on to the opposing surfaces ofmembers A and B, said fluid being selected from the group consisting ofpetroleum hydrocarbons having a terminal boiling point no greater than345 C., aliphatic alcohols of 1-12 carbon atoms and aliphatic aldehydesof 4-9 carbon atoms; and moving said opposing surfaces relative to eachother whereby said fluid is polymerized to form a lubricating medium.

23. A process as in claim 22 wherein an oil is added with said fluid.

24. In a lubricating system composed of the opposing surfaces of atleast two members, members A and B, and a lubricating fluid present onsaid opposing surfaces, the improvement wherein the opposing surface ofmember A consists essentially of an alloy selected from the groupconsisting of (a) an alloy of 11-15 atom percent carbon,

1.53 atom percent silicon, the balance being substantially all iron,having a Vickers Hardness number of at least 150, (b) an alloy of atleast 80 atom percent iron and having a Vickers Hardness number of atleast 175, and (c) an alloy of at least 50 atom percent iron and havinga Vickers Hardness number of at least 400, the sum of any cobalt andnickel in said alloys (b) and (0) being less than 6 atom percent, atleast one-half of the weight of the remainder of alloys (b) and (c)being selected from the group of elements consisting of chromium,molybdenum, manganese and tungsten, said element(s) being present ascarbide(s) or in a fully hardened solid solution; and the opposingsurface of member B consists essentially of an alloy of at least 6 atompercent of an element selected from the group consisting of molybdenumand tungsten, at least 10 percent by volume of said alloy being anintermetallic compound of said element, the Vickers Hardness number ofsaid compound being 550-1800, and any matrix in said alloy containingsaid compound having a Vickers Hardness num ber less than that of saidcompound, the coefficient of dry friction of said surface of member Bagainst said surface of member A being no greater than 0.25.

References Cited US. Cl. X.R.

